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F4 FPU interrupt vector

Question asked by PICguy on Jul 24, 2014
Latest reply on Jul 25, 2014 by PICguy
STM32F4xxx Reference Manual, DM00031020 rev 6, has the “FPU” interrupt vector at position 81, address 0x00000184 (or 0x08000184 depending on how one views low ROM).  I found no documentation about what this vector is for.  I can only assume that it has something to do with the ARM fp co-processor included in ST’s F4xxx parts.

Would someone please say what this vector is all about.

I was able to catch fp instructions with a Usage Fault Exception interrupt.  Then (1) enable the fp co-processors, (2) save fp registers leftover from another task and (3) restore the saved fp registers for the current task.  Inelegant, but it works.  IIRC, the full save restore took fewer than 150 clocks from instruction trap to restarting the trapped instruction.